[Stultis]

Are there instances of "related" species using different codings to encode the amino acid sequences for the same protein? Or, despite the existence of codons which permit variability, do "related" species use the same codon sequence for the same proteins?

That later, overwhelmingly.

For instance there are many, many protein sequences in humans and chimpanzees that are identical, and their DNA sequences also identical or very nearly so, even though variations in other species allow for the same protein function. IOW there are loads and loads of gratuitous, completely unnecessary, overkill similarities between closely related species, with equally unnecessary dissimilarities as you go to evolutionary more distant species, all the time with the corresponding proteins equal in function and efficiency.

[count-your-change]

You know these sequences are “gratuitous, completely unnecessary, overkill”, how?